The present invention relates to a method for producing a 4-alkyl-3-methylenebutyl carboxylate that is useful as a bioactive substance such as an insect pheromone and substance relating thereto and as a synthetic intermediate in organic synthetic chemistry. For example, the present invention relates to a method for producing 7-methyl-3-methylene-7-octenyl propionate, which is, for example, a major component of the sex pheromone of Quadraspidiotus perniciosus (Comstock) (generic name: San Jose Scale).
The sex pheromones of insects are biologically active substances that are commonly secreted by female individuals and have the function of attracting male individuals. A small amount of the sex pheromone shows strong attractive activities. The sex pheromone has been widely used as means for forecasting insect emergence or for ascertaining regional spread (invasion into a specific area) and as means for controlling an insect pest. As the means for controlling insect pests, control methods called mass trapping, lure and kill (another name: attract and kill), lure and infect (another name: attract and infect), and mating disruption are widely used in practice. To utilize the sex pheromone, economical production of a required amount of the pheromone product is demanded for basic research and also for application.
Quadraspidiotus perniciosus (generic name: San Jose Scale, hereinafter abbreviated as “SJS”) is widely distributed in the world, damages fruit trees and ornamental trees, especially deciduous fruit trees, and thus is an economically critical insect pest. As for the sex pheromone of SJS, three compounds of 7-methyl-3-methylene-7-octenyl propionate, (Z)-3,7-dimethyl-2,7-octadienyl propionate, and (E)-3,7-dimethyl-2,7-octadienyl propionate have been identified as the active components by Gieselmann et al. (J. Chem. Ecol., 5, 891 (1979)).
These sex pheromone compounds of SJS are isomers to each other, and there is a demand for a selective production method of each compound for basic biological studies and agronomic studies. There is also a strong demand for an efficient production method capable of supplying a sufficient amount of the pheromone product for the purposes of application and practical use.
Examples of the synthesis of 7-methyl-3-methylene-7-octenyl propionate, which is the major component of the sex pheromone of SJS, include the following Syntheses (a) to (f):
Synthesis (a) comprising addition of an organocuprate reagent to alkyne as a key reaction, by Anderson et al. (J. Chem. Ecol., 5, 919 (1979));
Synthesis (b) comprising a one-carbon homologation step of a β-keto ester compound, 7-methyl-3-oxo-7-octenoate, by Weiler et al. (Can. J. Chem., 71, 1955 (1993));
Synthesis (c) comprising photochemical position isomerization of a double bond of an α,β-unsaturated ester to a β,γ-unsaturated ester as a key reaction, by Weeden et al. (Tet. Lett., 27, 5555 (1986));
Synthesis (d) comprising exo-methylene formation as a key reaction by reduction of an allylic chloride obtained by chlorination involving isomerization of a trisubstituted double bond, by Zhang et al. (Chinese Chemical Letters, 2, 611 (1991), Huaxue Tongbao, 40, (1994));
Synthesis (e) by alkylation of a dianion of 3-methyl-3-buten-1-ol, by Anderson et al. (J. Chem. Ecol., 5, 919 (1979)) and Chong et al. (J. Org. Chem., 66, 8248 (2001)); and
Synthesis (f) which is a nonselective synthesis through an allylic chloride mixture, by Veselovskii et al. (Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 3, 513 (1990)).